METABOLISM OF ESFENVALERATE BY PYRETHROID-SUSCEPTIBLE AND PYRETHROID-RESISTANT AUSTRALIAN HELICOVERPA-ARMIGERA (LEPIDOPTERA, NOCTUIDAE)

Esfenvalerate metabolism in pyrethroid-resistant and -susceptible Australian Helicoverpa armigera larvae was studied using in vivo and in vitro methods. Data from both methods showed very little evidence of esfenvalerate metabolism in the susceptible strain. In a resistant strain, esfenvalerate metabolism was only slightly enhanced, as evidenced by traces of several labelled and nonlabelled metabolites in the excreta and internal fractions. Piperonyl butoxide did not inhibit this metabolism; however, there was evidence that it may facilitate esfenvalerate penetration in the resistant insects, presumably, increasing the available internal dose. Reduced penetration of esfenvalerate appeared to be an important resistance mechanism in the resistant strain. (C) 1995 Academic Press, Inc.